First generation ethanol fermentation facilities produce ethanol from starch-based feedstock such as corn. In a typical conventional corn-to-ethanol fermentation process, starch present in corn is broken down into simple sugars, which can be fermented by an ethanologen such as yeast into ethanol.
Traditional ethanol production processes typically involve five basic steps: milling, cooking, saccharification, fermentation, distillation and recovery. In some such processes, the milling step is a dry milling step in which corn is ground into flour. Cooking may involve mixing the flour with water to form a slurry, heating the slurry to above the gelatinization temperature of the corn, and treating the slurry with a liquefying enzyme to hydrolyze starch contained therein to dextrins. In the saccharification step, enzymes are added to the mash to convert the corn starch into simple sugars. The fermentation of the sugars by an ethanologen such as yeast produces a beer, which is separated into ethanol and whole stillage by distillation. The whole stillage may be subject to further processing wherein it is separated into wet cake and thin stillage. The thin stillage passes through evaporators to produce a syrup, which may be recombined and dried with the wet cake to produce distillers grains with solubles (DDGS), an animal feed. Not all dry mill ethanol production processes involve all the identified steps. For example, in some dry mill ethanol production processes, saccharification and fermentation are not independent steps but occur simultaneously. As another example, some dry mill ethanol production processes do not involve liquefaction. As yet another example, POET®'s BPX® hydrolysis process does not use a jet cooker (i.e. a cooking step).
In order to produce a pure sugar stream while also making other components of corn available to sell, some conventional processes use a wet mill rather than dry mill approach. In wet milling, corn is soaked in water to soften the grain and facilitate separating the various components of the corn kernel. After “steeping”, various components such as starch, fiber and germ are separated from one another for separate processing into a variety of products. Fractionation equipment, however, is expensive and increases the cost of producing the sugar stream.